6,343 research outputs found
Symmetry Reduction and Boundary Modes for Fe-Chains on an s-wave Superconductor
We investigate the superconducting phase diagram and boundary modes for a
quasi-1D system formed by three Fe-Chains on an s-wave superconductor,
motivated by the recent Princeton experiment. The onsite
spin-orbit term, inter-chain diagonal hopping couplings, and magnetic disorders
in the Fe-chains are shown to be crucial for the superconducting phases, which
can be topologically trivial or nontrivial in different parameter regimes. For
the topological regime a single Majorana and multiple Andreew bound modes are
obtained in the ends of the chain, while for the trivial phase only low-energy
Andreev bound states survive. Nontrivial symmetry reduction mechanism induced
by the term, diagonal hopping couplings, and magnetic
disorder is uncovered to interpret the present results. Our study also implies
that the zero-bias peak observed in the recent experiment may or may not
reflect the Majorana zero modes in the end of the Fe-chains.Comment: 5 pages, 4 figures; some minor errors are correcte
Reducing the Tension Between the BICEP2 and the Planck Measurements: A Complete Exploration of the Parameter Space
A large inflationary tensor-to-scalar ratio is reported by the BICEP2 team based on their B-mode
polarization detection, which is outside of the confidence level of the
Planck best fit model. We explore several possible ways to reduce the tension
between the two by considering a model in which ,
, and the neutrino parameters and
are set as free parameters. Using the Markov Chain
Monte Carlo (MCMC) technique to survey the complete parameter space with and
without the BICEP2 data, we find that the resulting constraints on
are consistent with each other and the apparent tension
seems to be relaxed. Further detailed investigations on those fittings suggest
that probably plays the most important role in reducing the
tension. We also find that the results obtained from fitting without adopting
the consistency relation do not deviate much from the consistency relation.
With available Planck, WMAP, BICEP2 and BAO datasets all together, we obtain
, ,
, and
; if the consistency relation is
adopted, we get .Comment: 8 pages, 4 figures, submitted to PL
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